Naomi Maruyama

First forecast of a sudden stratospheric warming with a coupled whole‐atmosphere/ionosphere model IDEA

We present the first “weather forecast” with a coupled whole-atmosphere/ionosphere model of Integrated Dynamics in Earths Atmosphere (IDEA) for the January 2009 Sudden Stratospheric Warming (SSW). IDEA consists of the Whole Atmosphere Model and Global Ionosphere-Plasmasphere model. A 30 day forecast is performed using the IDEA model initialized at 0000 UT on 13 January 2009, 10 days prior to the peak of the SSW. IDEA successfully predicts both the time and amplitude of the peak warming in the polar cap. This is about 2 days earlier than the National Centers for Environmental Prediction operational Global Forecast System terrestrial weather model forecast. The forecast of the semidiurnal, westward propagating, zonal wave number 2 (SW2) tide in zonal wind also shows an increase in the amplitude and a phase shift to earlier hours in the equatorial dynamo region during and after the peak warming, before recovering to their prior values about 15 days later. The SW2 amplitude and phase changes are shown to be likely due to the stratospheric ozone and/or circulation changes. The daytime upward plasma drift and total electron content in the equatorial American sector show a clear shift to earlier hours and enhancement during and after the peak warming, before returning to their prior conditions. These ionospheric responses compare well with other observational studies. Therefore, the predicted ionospheric response to the January 2009 SSW can be largely explained in simple terms of the amplitude and phase changes of the SW2 zonal wind in the equatorial E region.

A real‐time run of the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model

[1] The availability of unprecedented amounts of real-time data from Global Navigation Satellite Systems and ionosondes coupled with new and more stringent requirements for specification and forecast of the neutral and electron densities in the thermosphere-ionosphere system are driving a new wave of development in data assimilation schemes for the thermosphere and ionosphere. However, such schemes require accurate knowledge of any biases affecting the state-propagating models, and characterizing such biases involves significant effort. A first step in the estimation of the model biases, a steady state neutral temperature comparison with the empirical Mass Spectrometer Incoherent Scatter model, was published in Space Weather in 2008. Here we present another step in the validation of the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) general circulation model in preparation for its future inclusion in a data assimilation scheme. We describe an implementation of the model at the Space Weather Prediction Center (SWPC) and present real-time comparisons between CTIPe and GPS total electron content and F2 layer ionosonde measurements. The CTIPe results are generated automatically about 20 min ahead of real time. The model inputs are based on NASA’s Advanced Composition Explorer and F10.7 data available in the SWPC database. The results and the comparison with measurements for the current 2-week period are available at http://helios.swpc.noaa.gov/ctipe/. The results are quite encouraging and offer hope that physics-based models can compete with empirical models during quiet times and have tremendous potential to provide more reliable forecasts during periods of geomagnetic disturbance.

Modeling the Storm Time Electrodynamics

A model that electrodynamically couples inner magnetosphere, ionosphere, plasmasphere, thermosphere, and electrodynamics has been developed and is used to separate sources of the storm time electric fields between the magnetospheric, ionospheric, and thermospheric processes and to investigate their nonlinear interactions. The two sources of the electric-field disturbances, prompt penetration (PP) and disturbance dynamo (DD), have been identified in the coupled model results. Furthermore, the results suggest that the sources of variability in storm time electric fields are associated with the nonlinear interaction between the PP and DD, such that the response depends on the preconditioning of the coupled system. The preconditioning in this study is caused by the fact that the magnetosphere, ionosphere, and thermosphere respond to external forcing as a coupled system. The results clearly demonstrate the need for a fully coupled model of magnetosphere–ionosphere–thermosphere, in order to determine the preconditioning effect.

Field‐aligned neutral wind bias correction scheme for global ionospheric modeling at midlatitudes by assimilating FORMOSAT‐3/COSMIC hmF2 data under geomagnetically quiet conditions

This study demonstrates the usage of a data assimilation procedure, which ingests the FORMOSAT-3/COSMIC (F3/C) hmF2 observations to correct the model wind biases to enhance the capability of the new global Ionosphere Plasmasphere Electrodynamics (IPE) model under geomagnetically quiet conditions. The IPE model is built upon the field line interhemispheric plasma model with a realistic geomagnetic field model and empirical model drivers. The hmF2 observed by the F3/C radio occultation technique is utilized to adjust global thermospheric field-aligned neutral winds (i.e., a component of the thermospheric neutral wind parallel to the magnetic field) at midlatitudes according to a linear relationship between time differentials of the field-aligned wind and hmF2. The adjusted winds are further applied to drive the IPE model. The comparison of the modeled electron density with the observations of F3/C and ground-based GPS receivers at the 2012 March equinox suggests that the modeled electron density can be significantly improved in the midlatitude regions of the Southern Hemisphere, if the wind correction scheme is applied. Moreover, the F3/C observation, the IPE model, and the wind bias correction scheme are applied to study the 2012 Southern Hemisphere Midlatitude Summer Nighttime Anomaly (southern MSNA)/Weddell Sea Anomaly (WSA) event at December solstice for examining the role of the neutral winds in controlling the longitudinal variation of the southern MSNA/WSA behavior. With the help of the wind bias correction scheme, the IPE model better tracks the F3/C-observed eastward movement of the southern MSNA/WSA feature. The apparent eastward movement of the southern MSNA/WSA features in the local time coordinate is primarily caused by the longitudinal variation in the declination angle of the geomagnetic field that controls the field-aligned projection of both geographic meridional and zonal components of the neutral wind. Both the IPE simulations and the F3/C observations show the significant longitudinal variation in the speed of the eastward movement of the southern MSNA/WSA.

A new source of the midlatitude ionospheric peak density structure revealed by a new Ionosphere‐Plasmasphere model

The newly developed Ionosphere-Plasmasphere (IP) model has revealed neutral winds as a primary source of the “third-peak” density structure in the daytime global ionosphere that has been observed by the low-latitude ionospheric sensor network GPS total electron content measurements over South America. This third peak is located near −30° magnetic latitude and is clearly separate from the conventional twin equatorial ionization anomaly peaks. The IP model reproduces the global electron density structure as observed by the FORMOSAT-3/COSMIC mission. The model reveals that the third peak is mainly created by the prevailing neutral meridional wind, which flows from the summer hemisphere to the winter hemisphere lifting the plasma along magnetic field lines to higher altitudes where recombination is slower. The same prevailing wind that increases the midlatitude density decreases the low-latitude density in the summer hemisphere by counteracting the equatorial fountain flow. The longitudinal variation of the three-peak structure is explained by the displacement between the geographic and geomagnetic equators.